In recent years the availability of inexpensive LEDs in an increasing variety of colors, brightness, and size has led to the development of LED displays for purposes of amusement or ornamentation. For example, earrings, necklaces, pendants, headbands, hats, blouses and shirts have been adorned with LED displays powered by small portable batteries. Often the LEDs are driven by a simple oscillator circuit to switch on and off and attract the attention of the casual observer. Generally, these devices are limited to small-scale displays.
LEDs have also been used for other forms of mini-light style ornamental display, such as Christmas tree light strings, LED illumination for doll houses and miniatures, and the like. Often these devices are driven by complex circuitry that generates an oscillating signal to switch the LEDs off and on at various rates, as well as to combine the discrete colors of various LEDs to create the illusion of a wide range of colors. Although these devices are successful in creating the desired amusement displays, they generally involve many kinds of integrated circuit chips and other electronic components to generate the oscillator frequency.
An unused source of oscillator frequencies for light displays exists in the invisible fields surrounding AC lines and equipment. There are at present several AC voltage sensors commercially available which use a CMOS hex inverter to activate a single LED and a speaker. These circuits attach an antenna to one of the six possible inputs to the inverter and add capacitors and resistors to modulate the pulse. These circuits are functional only as test instruments and have no ornamental value. In addition to the ornamental and visible timing features of the present invention, there is the additional advantage of a built-in ON indicator. In the battery operated mode, the circuit will always have one LED illuminated when the device is not receiving an electromagnetic field signal. All of the LEDs are driven to flicker when the device receives an EMF signal.